It is known from prior art to comminute pieces of material, for example of concrete or rock, by means of pulsed high voltage discharges or to weaken them by means of pulsed high voltage discharges, i.e. to produce cracks in them so that in a subsequent mechanical comminution process it is easier to comminute them.
For doing so, the material that is to be fragmented or weakened, respectively, together with a process liquid, for example water, is introduced into a process area, inside which between two electrodes high voltage discharges are generated. In this process, generally two different modes of action are differentiated.
In the so called electrohydraulic acting upon the material that is to be fragmented or weakened, respectively, the discharging path runs exclusively through the process liquid, so that shock waves are produced within the process liquid which act upon the material that is to be fragmented or weakened, respectively. This mode of action however has the disadvantage, that only a small amount of the energy required for generating the high voltage discharges serves for the fragmentation or weakening of the material, respectively. Accordingly, in the electrohydraulic acting mode, for achieving relative modest fragmentation or weakening results, respectively, large amounts of energy are required, the provision of which furthermore is associated with a high expenditure on the equipment side. Furthermore, the fragmentation or weakening of relative hard materials is practically not possible by means of the electrohydraulic mode of action.
In the so called electrodynamic acting mode, the discharging path runs at least partially through the material that is to be fragmented or weakened, respectively, so that inside the material itself a shock wave is generated. With this mode of action, a considerable larger portion of the expended amount of energy can be deployed for the fragmentation or weakening of the material than in the electrohydraulic acting mode, and also considerably harder materials can be fragmented or weakened, respectively.
However, also in the electrodynamic methods known today the energy efficiency and the capability of fragmentation or weakening, respectively, hard and brittle materials cannot be considered as being satisfactory. Also it has shown that in the methods of fragmenting or weakening, respectively, of materials by means of high voltage discharges known today, with some materials, like e.g. concrete, after an initially predominant electrodynamic acting upon the material, relative quickly it comes to a change to a substantially electrohydraulic acting, resulting in the effect that the effectiveness of the fragmentation or weakening process, respectively, decreases rapidly or the high voltage discharges at the worst cause no fragmentation or weakening of the material at all. Due to this phenomenon such methods today are uneconomical or even unsuitable for certain materials.